1. Field of the Invention
The present invention relates to improvements in a cuvette rotor assembly utilized in a multistation photometric analyzer of the type wherein several chemical reactions are sequentially monitored over a predetermined time span. More specifically, the present invention is directed to an improved cuvette rotor used in the assembly.
2. Description of the Prior Art
Heretofore, multistation photometric analyzers of the type wherein several chemical reactions are sequentially monitored over a predetermined time span have been proposed. In such analyzers a central transfer disc having a plurality of spoke like channels therein with each channel having three wells, is situated within a ring shaped cuvette rotor having an outer circular periphery, an inner circular periphery, a first side, a second side and cuvette forming slots extending between the sides and into the rotor from the inner periphery toward the outer periphery. Glass windows are situated on either side of the cuvette rotor and a fixed beam of light is directed toward one side of the rotor through the windows and through the cuvettes.
The inner well in each channel in the transfer disc receives a reagent or a sample and the middle well receives sample or reagent. When a reaction between a reagent and a sample is to be monitored, the transfer disc and the cuvette rotor are rotated. Centrifugal force then urges the liquid in the inner well into the middle well and then both liquids are urged by centrifugal force into the outer well where they are mixed. Further, the centrifugal force then urges the mixed liquid from the outer mixing well into one of the cuvettes. Then, each time that particular cuvette passes the fixed beam of light, the light that passes through the cuvette as the reaction is taking place therein is sensed and measured.
Examples of photometric analyzers of the type described above are disclosed in the following U.S. Patents:
______________________________________ U.S. Pat. No. PATENTEE ______________________________________ 3,514,613 Mashburn 3,536,106 Anderson 3,547,547 Anderson 3,555,284 Anderson 3,582,218 Anderson 3,586,484 Anderson 3,856,470 Cullis et al. ______________________________________
In the Cullis et al. U.S. Pat. No. 3,856,470 referred to above, there is disclosed a rotor apparatus wherein an electric heating element is secured by an adhesive to a ring shaped cuvette rotor in order to heat the mixture of reagent and sample in the cuvettes to optimum temperature and to maintain the mixtures at that temperature during the reaction time.
The previously proposed cuvette rotors and cuvette rotor assemblies including same have functioned very well in enabling a photometric analyzer incorporating same to monitor reactions between a reagent and a sample over a predetermined time period. However, difficulties have been incurred in manufacturing the cuvette rotor and in the assembly including same. In this respect, a number of operations had to be performed on the cuvette rotor before it was ready for final assembly in a cuvette rotor assembly. This required shipping and handling of the rotor. Since the rotor was made of a soft copper material, the shipping and handling of the rotor as well as the various operations that were performed thereon often resulted in warping of the rotor and therefore rejection of same.
More specifically, the cuvette rotors heretofore utilized in photometric analyzers of the type sold under the trademark Rotochem by American Instrument Company of Silver Spring, Md., a Division of Baxter Travenol Laboratories, Inc., were made of solid "dead" copper, which is very soft material. Once the copper rotor was obtained from the manufacturer, it was sent out for machining. Then, when it came back from machining, it was sent out for nickel plating. After it was plated and returned, it was then sent out for securing a heating element thereto. It will be appreciated that the sending out of the cuvette rotor for coating, for finishing and for securing a heating element thereto, of necessity, required handling of the rotor which caused warping. Accordingly, each time the rotor was returned from an operation performed thereon, it had to be measured to see if it had warped.
Also, the previously utilized copper cuvette rotors did not provide a convenient means for monitoring the temperature of the rotor.
With a view toward overcoming these disadvantages incurred with the previously utilized copper cuvette rotors and as will be described in greater detail hereinafter, the present invention provides a cuvette rotor assembly including a cuvette rotor which is made of a harder copper alloy material and which is dimensioned so as to provide a cuvette rotor having a greater width between the inner and outer peripheries thereof. Also, the heating element is secured mechanically by fasteners so that the step of sending the cuvette rotor out for having an electric heating element secured thereto by an adhesive is eliminated.